For all of you guys that make laminated bows is there a chart comparing the thickness of a bow with the poundage. I guess what I am asking is how do you know how thick to make the lams for any given weight of bow.

It all depends on the bow design including bow length, profile, limb width, etc. etc. Any chart available is only good for that exact bow design. The Binghams catalog has charts in the back but they are only good for their designs. Change an element of the design and the charts are no good. If your design is close to theirs it may be a good starting point but it's my understanding that trial and error is the only way to know for sure.

Three Rivers has a chart you can download.Go to their lamination section on the net catalog. I don't know how good/accurate it is and I'm sure it depends on your form some too. I will tell ya in a couple of weeks though. I have some old laminations from an old Bingham project but I couldn't find my plans in storage so I bought a longbow plan from 3 rivers  and I'm going to use the lams I have and use their plan chart to figure out how much poundage it may come out. LOL! No matter anyway since I bought the lams years ago. If ya cant find the chart, get back with me and I will send you a link!

I was looking for some general guidelines, sort of a starting point when designing a bow.

I use to have one for a 66" r/d longbow.  I got the chart from Old Master crafters many years ago.  It was right on for a fairly mild (todays standards) LB.

If I can find it I'll post it.

Carl

This is from Bingham Projects
Bow Draw Weight Charts





All draw weights determined at 28" draw length.

Bow draw weights will not be the same if bow design, bow length, bow width or riser length is changed.

58" Recurve Bow



(measured at thickest point/center of limb)



1 3/4" Limb Width



30# ‑ 34#  .240"

38# ‑ 42#  .250"

46# ‑ 50#  .260"

54# ‑ 58#  .270"

62# ‑ 66#  .280"



2" Limb Width



30# ‑ 34#  .230"

38# ‑ 42#  .240"

46# ‑ 50#  .250"

54# ‑ 58#  .260"

62# ‑ 66#  .270"



60" Recurve Bow



(measured at thickest point/center of limb)



1 3/4" Limb Width



30# ‑ 34#  .250"

38# ‑ 42#  .260"

46# ‑ 50#  .270"

54# ‑ 58#  .280"

62# ‑ 66#  .290"



2" Limb Width



30# ‑ 34#  .240"

38# ‑ 42#  .250"

46# ‑ 50#  .260"

54# ‑ 58#  .270"

62# ‑ 66#  .280"

_________________________



Take-Down Recurve



58" Take-Down Recurve



(measured at thickest point without

wedge inserted)



1 3/4" Limb Width



35#  .204"

40#  .212"

45#  .220"

50#  .226"

55#  .232"

60#  .240"

65#  .246"

70#  .252"













Note:

Add .015" for 60" Take-Down Recurve

Add .030" for 62" Take-Down. Recurve

58", 60" & 62" Take-Down Recurve bow

use 8 1/4" wedge



64" Take-Down Recurve



1 3/4" Limb Width



(measured at thickest point without

wedge inserted)



35#  .221"

40#  .228"

45#  .234"

50#  .240"

55#  .247"

60#  .255"

65#  .261"

70#  .267"



Note:

Add .015" for 66" Take-Down Recurve

Add .030" for 68" Take-Down. Recurve

64", 66" & 68" Take-Down Recurve bow

use 10 1/4" wedge



2" Limb Width



58" Take-Down Recurve



(measured at thickest point without

wedge inserted)



35#  .199"

40#  .205"

45#  .212"

50#  .219"

55#  .225"

60#  .230"

65#  .236"

70#  .242"



Note:

Add .015" for 60" Take-Down Recurve

Add .030" for 62" Take-Down Recurve

58", 60" & 62" Take-Down Recurve bow

use 8 1/4" wedge





2" Limb Width



64" Take-Down Recurve



(measured at thickest point without

wedge inserted)



35#  .215"

40#  .222"

45#  .228"

50#  .233"

55#  .239"

60#  .245"

65#  .251"

70#  .257"



Note:

Add .015" for 66" Take-Down Recurve

Add .030" for 68" Take-Down. Recurve

64", 66" & 68" Take-Down Recurve bow

use 10 1/4" wedge





68" Longbow



(measured at thickest point/center of limb)



35#  .344"

40#  .359"

45#  .374"

50#  .389"

55#  .404"

60#  .418"

65#  .427"

70#  .435"

_____________________



68" Take-Down Longbow



(measured at thickest point without

wedge inserted)



 Shallow

                   

35#  .328"

40#  .344"

45#  .359"

50#  .374"

55#  .389"

60#  .404"

65#  .418"

70#  .427"        



Pronounced



35#  .260"

40#  .275"

45#  .290"

50#  .305"

55#  .320"

60#  .335"

65#  .350"

70#  .365"



All Take-Down Longbows use

8 1/4" wedge.

The Binghams chart is as good as any, but the only thing they can really do for you is keep you from building a 100+ pounder the first try.  Any changes to the formula change the chart.  Longer riser, siffer fades, wider/narrower limbs can all change the outcome on the same form.  When you change the form (read limb geometry) you are taking an educated guess until you build one.  After that, between .002 and .003 change in thickness will give you about one pound in draw weight change for most longbow designs.  But that is just a general guideline.  It usually takes a few bows out of a given form to get the charts close.  It also varies more when you get out at either end of normal bow weights.